Sealed wire rope and strand and method of making same

ABSTRACT

A wire rope or strand is provided with a plastic foam type internal sealant to cushion the wires and strands and provide corrosion protection.

United States Patent 1151 3,681,91 l Humphries 14 1 Aug. 8, 1972 [54]SEALED WIRE ROPE AND STRAND [56] Referemes Cited AND METH D MAKIN AME lt g H G 8 All I UNITED STATES PATENTS nven or: umphrles,

Pa, 3,370,045 2/1968 l7/l28.4 x 3,463,652 8/1969 Whitesel et al..........57/149 X Asslsnw Bethlehem Steel Corporation 3,507,741 4/1970Aleixo .....................57/153 x 22 Filed: March 3 197 3,589,1216/1971 Mulvey ..57/I49 X [21] Appl. No.: 112,211 FOREIGN PATENTS ORAPPLICATIONS 789,163 1/1958 Great Bn'tain ..57/ 153 954,514 4/1964 GreatBritain ..57/149 [63] Continuation-impart of Ser. No. 850,148, Aug.

14, 1969, abandoned. Primary Examiner-Donald E. Watkins Attorney-JosephJ. O'Keefe [52] US. Cl. ..57/149, 57/153, 57/162,

57/164, 161/175, 117/128 [57} ABSTRACT E33 s A wire rope or strand isprovided with a plastic foam 57/162, 164; 161/172, 175; ll7/l27, 128,128.4, 128.7, 132, 133

type internal sealant to cushion the wires and strands and providecorrosion protection.

16 Claim, 12 Drawing Figures SEALED WIRE ROPE AND STRAND AND METHOD OFMAKING SAME CROSS-REFERENCES TO RELATED APPLICATIONS This application isa continuation-in-part of U. 8. application Ser. No. 850,148 filed Aug.14, 1969, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to the sealing ofwire rope and strand for protection against corrosive environments.

Steel wires and strands are subject to internal corrosion of wires dueto the entrapment of water within the structure of the strand betweenthe individual wires.

Various expedients have been used to bar the entrance of the waterincluding the provision of heavy lubricants, external plastic coatingand encapsulation of the individual wires, strands, or even an entirewire rope, in solid plastic sheaths. Lubricants are soon lost from anotherwise unprotected rope or strand. External coatings and sheaths aresubject to wear, and upon rupture of the sheath at any point will admitmoisture to the entire strand or rope. Solid encapsulation of a rope orstrand on the other hand not only makes the structure too stiff andinflexible for many uses but is also difficult to attain.

Encapsulation of individual wires prior to fabrication also results inconsiderable stiffening of a rope subsequently fabricated from the wiresand the wire density in the rope is undesirably reduced by theadditional thickness of the plastic. In addition the corrosionprotection afforded to the wires by the plastic polymer coating is lostif the coating is damaged during rope or strand manufacture, a rathercommon occurrence.

Various expedients have been tried to alleviate the foregoingdifficulties but none has heretofore been completely successful. Thepresent invention prevents the entrance into and migration of moisturein liquid or vapor form through a wire rope or strand while avoiding theforegoing disadvantages of the prior art.

SUMMARY OF THE INVENTION In the practice of the present invention theindividual wires or strands of a strand or rope are initially coatedwith a heat foamable plastic composition and subseq uently afterfabrication of the wires or strand into a wire rope the body of the ropeis heated while confined within a conforming mold to expand the plasticinto a substantially closed cell plastic foam. The plastic foam is lightand flexible, prevents the entrance and migration of moisture into andthrough the internal portions of the rope, provides a cushion for thestrands and does not significantly decrease wire density in the strandor rope. The plastic foam also acts as a vibration damper when the ropeis subjected to fluctuating loads in service. Since the foaming of theplastic is not carried out until the fabrication of the rope or strandhas been completed the foam plastic coating on the wires is selfhealingand any damage to the plastic during fabrication of the strand or ropeis healed over during the foaming step. A plastic foam coating,furthermore, is economical due to the low average density of the plasticfilling between the wires and strands of the rope. A dense outer layerof denser wear resistant plastic encapsulates the foam filled rope orstrand.

2 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows afabrication line for parallel wire strand incorporating a plastic foamsealing step.

FIG. 2 is a cross-sectional elevation of a portion of FIG. 1 showing aplastic coating bath.

FIG. 3 is an enlarged cross-sectional view along line 3-3 of FIG. 1.

FIG. 4 is an enlarged cross-sectional view along line 4-4 of FIG. 1.

FIG. 5 is an enlarged cross-sectional view along line 5-5 of FIG. 1.

FIG. 6 shows a section of wire rope undergoing a batch type foamingoperation.

FIG. 7 is an enlarged cross-section along 7-7 of FIG. 6.

FIG. 8 is an enlarged cross-section along 88 of FIG. 6.

FIG. 9a is an enlarged cross-section along 9-9 of FIG. 6.

FIG. 9b is a further enlarged half section of FIG. 90.

FIG. 10 is a schematic representation of an apparatus for continuouslyfoaming plastic in wire rope.

FIG. 11 is a cross-sectional view along 11- of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. I is shown a parallelwire strand fabrication line adapted for the production of foam filledparallel wire strand.

Two groups of reels II and 13 rotatable in opposite directions arearranged to provide wires 15 and 17 for fabrication into a parallel wirestrand. Wires 15 from reels II are guided by small guide plates 19 toplastic coating chamber 23 where the wires are coated with a foamableplastic composition. Wires 17 from reels 13 are in like manner guided tocoating chamber 23 by guide plates 25. The wires 15 and 17 may be coatedin chamber 23 in any convenient manner, but as illustrated the wires aredeflected by guide rollers 27 within chamber 23 into and below thesurface of a bath of a foamable plastic composition 28. The bath iscomposed of a suspension or solution of foamable plastic material in asolvent. The wires 15 and 17 then pass through wiping dies 29 located inthe side of coating chamber 23 and pass to drying chamber 31 where thefoamable composition is firmly dried upon the individual wires byexposure to a low heat to evaporate the solvent from the plasticcomposition and form a coating 30 of foamable plastic upon theindividual wires. As the wires pass from coating chamber 23 to dryingchamber 31 they may be exposed to an air blast from compressed airnozzle 33.

From drying chamber 31 the wires 15 and 17 with coatings 30 pass througha series of converging lay plates 35, 37 and 39 which direct the twogroups of wires into a first die 41. Die 41 may be a roller type die toreduce friction. Lay plates 35, 37 and 39 will desirably haveanti-friction surfaces within their guide holes such aspolytetrafluorethylene inserts or even roller type bearing surfaces inorder not to scrape the solidified foamable plastic coating 30 from thewires.

The wires 15 and 17 pass from die 41 to an identical die 43. The wiresare formed in these two dies into a parallel wire strand 45. Preferablydies 41 and 43 will have a hexagonal cross-section so as to form ahexagonal parallel wire strand as disclosed in U. S. application Ser.No. 575,038, filed Aug. 26, 1966, now U. S. Pat. No. 3,5 26,570, issuedSept. 1, 1970, by Durkee et al. for Parallel Wire Strand. The hexagonalshape of the strand 45 aids in obtaining an effective grip upon all thewires of the strand to pull them evenly through the dies and preventrotation of the wires as taught in the referred to application. It willbe understood, however, that the cross-sectional shape of the strand maytake other configurations besides hexagonal if the exact disposition ofthe wires in the strand is not critical in the parallel wire strandbeing fabricated.

1n the dies 41 and 43 the wires of the strand are subjected toconsiderable transverse force which deforms the foamable plastic coating30 on the wires at the contact line between the wires so that theresultant strand has a high wire density with a minimum separationbetween the bodies of the wires.

From die 43 strand 45 passes to mold 47 which may be formed from somedielectric substance such as hard rubber, plastic or other similarcomposition. Preferably mold 47 is water-cooled through inlet pipe 49and hose 49a and outlet pipe 51 and hose 51a. Within the mold thecooling water flows through cooling pipes 50 shown in FIG. 4. Mold 47has an internal cross-section identical in size and shape with the shapeand outside dimensions of the parallel wire strand 45.

Induction heating rings 53 surround the initial sections of mold 47 toheat the wires of the strand therein to a temperature sufficient to meltthe plastic coating 30 on the wires and cause the foaming agent thereinto expand the plastic into a plastic foam 55. The strand 45 then passesthrough the portion 57 of the mold 47 through which the cooling waterinitially passes and about which no induction heating coils aredisposed. The strand 45 and foamed plastic 55 are cooled in this sectionof the mold to set the plastic.

The strand 45 then passes from mold 47 to dies 59 and 61, which arepreferably roller type dies, and is wrapped between the dies at spacedintervals along the strand as it passes between the two dies with aplastic tape or other securing means to maintain the shape of thestrand. The wrapping may be applied manually or by means of any suitableautomatic wrapping machine.

After the wrapped strand passes through die 61 it passes to any suitablecatapuller device 63 which serves to pull wires and 17 and the strand 45from the respective reels and through the previous apparatus. Fromcatapuller 63 the strand passes through a traverse device 65 and isreeled onto a large diameter reel 67.

As the strand passes through mold 47 its component internal wires areheated by currents induced in the wires by the conduction coils and theplastic composition on the wires foams as shown in FIG. 4 and is thencooled into a permanent plastic foam seal 69 between the internal wiresof the strand as shown in FIG. 5. The cooled close-fitting internalsurface of the mold 47 prevents the plastic on the wires at the surfaceof the strand from foaming to any significant degree, forms a thin layer5b of fairly dense solidified plastic near the surface of the strand asbest seen in FIG. 5, and forces the foamed plastic deep into the strandbetween the WlfeS.

The plastic foam 55 completely fills the interstices between the wireseffectively sealing the strand against the entrance into or migrationthrough the strand of any corrosive agents. The plastic foam 55 isflexible and has little bulk so that it neither interferes with theflexibility of the strand as in reeling upon reel 67 nor decreases thewire density within the strand significantly. The term wire density asused in this application refers to the amount of space in the strandphysically occupied by the component wires.

The plastic foam can be of any suitable composition such as a vinylplastic having an organic nitrogen compound such as azodicarbonamide asa foaming agent. This plastic when heated above the decompositiontemperature of the organic nitrogen compound decomposes into nitrogenand carbon dioxide and expands the plastic into a foam. Another suitablecomposition would be a foamable polyurethane consisting of athermosetting elastomer filled with expandable plastic beads. Whenexposed to heat the plastic of the beads softens and an entrapped gastherein expands the plastic into a foam. The polyurethane elastomermatrix provides cross linking. Any other plastic composition which isflexible, tough and adherent to metal may be used with a foaming agentto coat the strand.

In FIG. 6 is shown a section of fabricated wire rope 71. The individualwires 73 of the rope 71 have before fabrication into strands 75 beencoated with a plastic foamable composition 76 in some suitable mannersuch as, for instance, shown in FIG. 1. The strands 75 are then strandedinto the main rope 71 as is well known in the art.

Any section of the rope 71 which it is desired to impregnate withplastic foam may then be placed within mold 77 which is formed from adielectric material. The internal section of the mold has a spiralconfiguration conforming to the spiral arrangement of the strands 75 ofthe rope 71. The mold 77 is formed in two halves 79 and 81 so it may beconveniently placed around the strand and is provided with a spiralinternal configuration to conform with the helical lay of the strands ofthe rope. It may be convenient in some instances to form the mold frommore than two major sections in order to facilitate assembly over therope. If desired the mold may be water cooled, particularly if it is tobe used repetitively. If the mold is formed from hard molded rubber itwill conform quite well to the surface of the wire rope preventingfoaming of the plastic on the external surface of the rope and forcingthe major portion of foaming composition into the interior of thestrands and the interior of the rope between the strands.

In order to foam the plastic an induction coil 83 is passed over themold sections 79 and 81 after they are placed over the wire rope. Thisheats the individual wires and strands of the rope which in turn heatthe plastic foaming composition causing it to soften and become plasticand causing the foaming agent to expand and foam the plastic as seen inFIG. 8. FIG. 9a shows a section of rope 71 which has already been foamedin a previous step. The interstices between the strands 75 and betweenthe individual wires 73 within the strands are completely impregnatedwith a tough, flexible adherent plastic foam which completely excludescorrosive agents from the interior of the rope and strands and providesa cushion between the strands.

If as frequently occurs the original plastic coating on the individualwires has been damaged during stranding into the wire rope no damage isdone to the finished wire rope since any nicks or scratches on theplastic coating on the wires are completely healed over by the foamingstep and the individual strands and the in terstices between the strandsare completely filled with adherent plastic foam.

FIG. shows an apparatus adapted for the continuous impregnation of afinished helical wire rope with a foam composition as shown in FlG. 9a.A catapuller type mold apparatus 85 has a series of molded rubber molds87 attached to two endless chains 89 passing around sprocket wheels 91.The inner surface of each mold has a spiral configuration to match thesurface configuration of the rope. Sprocket wheels 91 may be powerdriven to effect or assist the passage of the rope 93 or the apparatusmay be driven by the passage of the rope. As the molds 87 are carriedaround sprockets 91 they close together over rope 93 as seen incross-section in FIG. 11, and the spiral configurations on their innersurface close over the strands of the rope. The spiral on each mold 87matches the spiral on adjacent molds so that the spiral configurationcontinues from one mold to the next to form a continuous spiral on thewalls of the mold opening matching the lay of the strands of the wirerope. The spiral configuration on the mold surfaces is arranged torepeat as consecutive full lay lengths of strand pass through the moldapparatus 85. Different sets of molds are attached to endless chains 89for different sized ropes and different rope lay lengths.

THe molded rubber molds 87 do not normally need to have auxiliarycooling as the molds are continuously exposed to the cooling effects ofthe atmosphere for at least half of each revolution of the catapullerapparatus and each provides a fairly effective heat sink to remove heatfrom the surface of the wire rope, particularly if carbon is included inthe rubber to increase the thermal conductivity.

A split induction coil 95 is mounted within the catapuller moldapparatus 85 surrounding the inner group of molds as they pass along themidline of the apparatus clamped together over the wire rope 93. As therope 93 passes through split induction coil 95 its individual wires andstrands are heated to melt and foam the surrounding plastic compositionto impregnate the strands with plastic foam and fill the interstices inthe interior of the rope between the strands with plastic foam. Therubber dielectric material of the molds 87 is not heated by theinduction coil 95 so that the outer surface of the rope is keptrelatively cool by the mold sections preventing excessive surfacefoaming and forming a thin layer 97 of fairly dense solidified plasticnear the surface of the strands as best shown in the finished rope inFIG. 9a and in FIG. 9b, an enlarged section of FIG. 9a, to prevent thefoam in the interior of the rope from escaping from the strands and ropeprior to complete solidification.

Other dielectric materials besides rubber can be used for the molds solong as they can be effectively con formed about the strand or rope andare sufficiently heat conductive. The strand could also, of course, be

heated by other means than induction heating such as by steam jackets orthe like and in suchcase the molds would not be required to be made froma dielectric material. Induction heating, however, is the mostconvenient and effective method of heating as it heats the strand orrope cross-section uniformly while allowing the surface to be kept coolto suppress excessive foaming in this area. Thus a solidified film orlayer 97 of dense plastic forms near the surface of the strand or ropeto contain the internal foam and provide a wear resistant plasticsurface. If induction heating is not used the strand and rope must beheated from the exterior necessitating a more tightly conforming mold onthe surface during heating to control the foaming, and a moresophisticated cooling section or cycle to confine the foam until anouter solidified layer of plastic 97 is formed.

The individual wires can be coated with the foaming composition in otherways than shown in F IGS. l and 2. ln addition to coating from a bath ofa suspension or emulsion of the plastic in a solvent, the wires can becoated by spraying, roller coating and other means. One particularlyeffective method of coating the wires with a thermoplastic coatingcomposition is by extrusion. The wire is passed through a pressureextrusion head which maintains the plastic under pressure as long as itis melted so that the foaming agent cannot expand. After extrusion ofthe coating on the wire the wire will usually be wound on a reel for useon a stranding machine. Thereafter the wires are stranded into wirestrand and ultimately in most cases into wire rope and the plasticfoamed either in the strand or the rope.

lclaim:

l. A wire strand having a tough, flexible plastic foam compositioncompletely filling the interstices between the wires of the strand andadherent to the wires to seal the strand against corrosive agents andmoisture and provide cushioning between the wires without significantreduction in wire density.

2. A wire rope having a tough, flexible plastic foam compositioncompletely filling the interstices between the wires of the strands andbetween the strands in the interior of the rope and adherent to the saidwires and strands to seal the strand against corrosive agents andmoisture and provide cushioning between the wires and the strandswithout significant reduction in wire density.

3. A plastic impregnated wire strand comprising:

a. a plurality of metallic wires stranded together,

b. a tough, flexible plastic foam composition filling the intersticesbetween the wires of the strand and adherent to the wires,

c. a solidified layer of dense plastic of substantially the samecomposition as the plastic foam of (b) adjacent to the surface of thestrand and encapsulating the plastic foam within the strand.

4. A plastic impregnated wire strand according to claim 3 wherein thewire density of the strand is not substantially less then the wiredensity of a similar unimpregnated wire strand having identical metalliccomponents and lay arrangement.

5. A wire strand according to claim 3 wherein the strand is a parallelwire strand.

6. A wire strand according to claim 3 wherein the strand is a helicalwire strand.

7. A wire strand according to claim 4 wherein the strand is a parallelwire strand.

8. A wire strand according to claim 4 wherein the strand is a helicalwire strand.

9. A plastic impregnated wire rope comprising:

a. a plurality of wire strands stranded together,

b. a tough, flexible plastic foam composition substantially completelyfilling the interstices between the wires of the component strands andbetween the strands in the interior of the rope and adherent to thewires,

c. a solidified layer of dense plastic of substantially the samecomposition as the plastic foam of (b) adjacent to the surface of therope and encapsulating the foam within the rope.

10. A plastic impregnated wire rope according to claim 9 wherein thewire density of the component strands of the rope is not substantiallyless then the wire density of a similar unimpregnated wire strand havingidentical metallic components and lay arrangement.

11. A method of fabricating a plastic foam impregnated wire strandcomprising:

a. coating the individual wires of the strand with a foamable plasticcomposition,

b. forming the wires into a strand, and

c. foaming the plastic foam composition within a closely confining moldsurrounding the strand by the application of heat to the strand.

12. A method of fabricating a plastic foam impregnated wire strandaccording to claim 11 wherein said strand is heated by induction-heatingmeans while confined within a mold composed of a dielectric material.

13. A method of fabricating a plastic foam impregnated wire strandaccording to claim 12 wherein said mold is cooled by a cooling agent.

14. A method of fabricating a plastic foam impregnated wire ropecomprising:

a. coating individual wires with a foamable plastic composition,

b. forming the coated wires into a strand,

c. forming the strands into a rope, and

d. foaming the plastic foam composition within a closely confining moldsurrounding the wire rope by the application of heat to the wire rope.

15. A method of fabricating a plastic foam impregnated wire ropeaccording to claim 14 wherein said rope is heated by induction-heatingmeans while confined within a mold composed of dielectric material.

16. A method of fabricating a plastic foam impregnated wire ropeaccording to claim 15 wherein said mold is cooled by a cooling agent.

1. A wire strand having a tough, flexible plastic foam compositioncompletely filling the interstices between the wires of the strand andadherent to the wires to seal the strand against corrosive agents andmoisture and provide cushioning between the wires without significantreduction in wire density.
 2. A wire rope having a tough, flexibleplastic foam composition completely filling the interstices between thewires of the strands and between the strands in the interior of the ropeand adherent to the said wires and strands to seal the strand againstcorrosive agents and moisture and provide cushioning between the wiresand the strands without significant reduction in wire density.
 3. Aplastic impregnated wire strand comprising: a. a plurality of metallicwires stranded together, b. a tough, flexible plastic foam compositionfilling the interstices between the wires of the strand and adherent tothe wires, c. a solidified layer of dense plastic of substantially thesame composition as the plastic foam of (b) adjacent to the surface Ofthe strand and encapsulating the plastic foam within the strand.
 4. Aplastic impregnated wire strand according to claim 3 wherein the wiredensity of the strand is not substantially less then the wire density ofa similar unimpregnated wire strand having identical metallic componentsand lay arrangement.
 5. A wire strand according to claim 3 wherein thestrand is a parallel wire strand.
 6. A wire strand according to claim 3wherein the strand is a helical wire strand.
 7. A wire strand accordingto claim 4 wherein the strand is a parallel wire strand.
 8. A wirestrand according to claim 4 wherein the strand is a helical wire strand.9. A plastic impregnated wire rope comprising: a. a plurality of wirestrands stranded together, b. a tough, flexible plastic foam compositionsubstantially completely filling the interstices between the wires ofthe component strands and between the strands in the interior of therope and adherent to the wires, c. a solidified layer of dense plasticof substantially the same composition as the plastic foam of (b)adjacent to the surface of the rope and encapsulating the foam withinthe rope.
 10. A plastic impregnated wire rope according to claim 9wherein the wire density of the component strands of the rope is notsubstantially less then the wire density of a similar unimpregnated wirestrand having identical metallic components and lay arrangement.
 11. Amethod of fabricating a plastic foam impregnated wire strand comprising:a. coating the individual wires of the strand with a foamable plasticcomposition, b. forming the wires into a strand, and c. foaming theplastic foam composition within a closely confining mold surrounding thestrand by the application of heat to the strand.
 12. A method offabricating a plastic foam impregnated wire strand according to claim 11wherein said strand is heated by induction-heating means while confinedwithin a mold composed of a dielectric material.
 13. A method offabricating a plastic foam impregnated wire strand according to claim 12wherein said mold is cooled by a cooling agent.
 14. A method offabricating a plastic foam impregnated wire rope comprising: a. coatingindividual wires with a foamable plastic composition, b. forming thecoated wires into a strand, c. forming the strands into a rope, and d.foaming the plastic foam composition within a closely confining moldsurrounding the wire rope by the application of heat to the wire rope.15. A method of fabricating a plastic foam impregnated wire ropeaccording to claim 14 wherein said rope is heated by induction-heatingmeans while confined within a mold composed of dielectric material. 16.A method of fabricating a plastic foam impregnated wire rope accordingto claim 15 wherein said mold is cooled by a cooling agent.